Polymetamorphism of the crystalline basement of the Somogy-Dráva basin (Southwestern Transdanubia, Hungary)
The crystalline basement of the Neogene depression of the Somogy—Drava Basin (SW-Transdanubia , Hungary) consists of medium-grade (almandine-amphibolite facies) polymetamorphic formation s overprinted by a very low- and low-grade (anchi-, epizonal) retrograde, partly cataclastic metamorphism: gneiss...
Elmentve itt :
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| Dokumentumtípus: | Cikk |
| Megjelent: |
University of Szeged, Department of Mineralogy, Geochemistry and Petrology
Szeged
1984
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| Sorozat: | Acta mineralogica-petrographica
26 No. 2 |
| Kulcsszavak: | Kőzettan, Ásványtan, Földtan |
| Tárgyszavak: | |
| Online Access: | http://acta.bibl.u-szeged.hu/24715 |
| Tartalmi kivonat: | The crystalline basement of the Neogene depression of the Somogy—Drava Basin (SW-Transdanubia , Hungary) consists of medium-grade (almandine-amphibolite facies) polymetamorphic formation s overprinted by a very low- and low-grade (anchi-, epizonal) retrograde, partly cataclastic metamorphism: gneiss, mica schist, amphibolite, as well as mylonite and blastomylonite. Having applied the petrological and geochemical methods of lithofacies reconstruction the gneiss — mica schist and the mylonite — blastomylonite groups developed from them proved to be of sedimentary (pára) origin: they were formed from carbonate-free or carbonate-poor pelitic-psammitic sediments. Th e amphibolite originated from basic igneous rock. On the basis of the mineral-paragenetic, petrotextural and structural as well as geothermometric and geobarometric characteristics the following relative chronological succession of metaniorphic events was determined: A ) Th e oldest one is a medium-grade (almandine-amphibolite facies), medium pressure (Harrovian) regional metamorphism with a geothermal gradient of 17 to 27 °C/km. Its temperature and pressure were 510 to 600 °C and 5.9 to 8.9 kbar, respectively. It was locally followed by B) an andalusite-type (low pressure range) medium-grade (amphibolite facies) metamorphism with a gradient =-34 °C/km and by C) a low temperature (<45 0 °C), predominantly low pressure anchi-, epizonal retrograde, locally cataclastic metamorphism. As to our recent knowledge —• based on Alpine and Carpathian analogies — different hypothetic geochronological modells can be established, e. g. — A) Caledonian, B) Hercynian, C) Hercynian and/or Alpine: — A) older Hercynian, B) younger Hercynian and C) younger Hercynian and/or Alpine: — A) Dalslandian (Early Baikalian), B) Hercynian, C) Hercynian and/or Alpine. T h e mineral assemblages formed b y weathering and by low temperature retrograde metamorphism were distinguished by means of the clay mineral associations and by the illite crystallinity. |
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| Terjedelem/Fizikai jellemzők: | 129-153 |
| ISSN: | 0365-8066 |